| Message ID | 20231108183003.5981-13-xin3.li@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Enable FRED with KVM VMX | expand |
On Wed, Nov 08, 2023 at 10:29:52AM -0800, Xin Li wrote: >Set injected-event data when injecting a #PF, #DB, or #NM caused >by extended feature disable using FRED event delivery, and save >original-event data for being used as injected-event data. > >Unlike IDT using some extra CPU register as part of an event >context, e.g., %cr2 for #PF, FRED saves a complete event context >in its stack frame, e.g., FRED saves the faulting linear address >of a #PF into the event data field defined in its stack frame. > >Thus a new VMX control field called injected-event data is added >to provide the event data that will be pushed into a FRED stack >frame for VM entries that inject an event using FRED event delivery. >In addition, a new VM exit information field called original-event >data is added to store the event data that would have saved into a >FRED stack frame for VM exits that occur during FRED event delivery. >After such a VM exit is handled to allow the original-event to be >delivered, the data in the original-event data VMCS field needs to >be set into the injected-event data VMCS field for the injection of >the original event. > >Tested-by: Shan Kang <shan.kang@intel.com> >Signed-off-by: Xin Li <xin3.li@intel.com> >--- > arch/x86/include/asm/vmx.h | 4 ++ > arch/x86/kvm/vmx/vmx.c | 84 +++++++++++++++++++++++++++++++++++--- > arch/x86/kvm/x86.c | 10 ++++- > 3 files changed, 91 insertions(+), 7 deletions(-) > >diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h >index d54a1a1057b0..97729248e844 100644 >--- a/arch/x86/include/asm/vmx.h >+++ b/arch/x86/include/asm/vmx.h >@@ -253,8 +253,12 @@ enum vmcs_field { > PID_POINTER_TABLE_HIGH = 0x00002043, > SECONDARY_VM_EXIT_CONTROLS = 0x00002044, > SECONDARY_VM_EXIT_CONTROLS_HIGH = 0x00002045, >+ INJECTED_EVENT_DATA = 0x00002052, >+ INJECTED_EVENT_DATA_HIGH = 0x00002053, > GUEST_PHYSICAL_ADDRESS = 0x00002400, > GUEST_PHYSICAL_ADDRESS_HIGH = 0x00002401, >+ ORIGINAL_EVENT_DATA = 0x00002404, >+ ORIGINAL_EVENT_DATA_HIGH = 0x00002405, > VMCS_LINK_POINTER = 0x00002800, > VMCS_LINK_POINTER_HIGH = 0x00002801, > GUEST_IA32_DEBUGCTL = 0x00002802, >diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >index 58d01e845804..67fd4a56d031 100644 >--- a/arch/x86/kvm/vmx/vmx.c >+++ b/arch/x86/kvm/vmx/vmx.c >@@ -1880,9 +1880,30 @@ static void vmx_inject_exception(struct kvm_vcpu *vcpu) > vmcs_write32(VM_ENTRY_INSTRUCTION_LEN, > vmx->vcpu.arch.event_exit_inst_len); > intr_info |= INTR_TYPE_SOFT_EXCEPTION; >- } else >+ } else { > intr_info |= INTR_TYPE_HARD_EXCEPTION; > >+ if (kvm_is_fred_enabled(vcpu)) { >+ u64 event_data = 0; >+ >+ if (is_debug(intr_info)) >+ /* >+ * Compared to DR6, FRED #DB event data saved on >+ * the stack frame have bits 4 ~ 11 and 16 ~ 31 >+ * inverted, i.e., >+ * fred_db_event_data = dr6 ^ 0xFFFF0FF0UL >+ */ >+ event_data = vcpu->arch.dr6 ^ DR6_RESERVED; >+ else if (is_page_fault(intr_info)) >+ event_data = vcpu->arch.cr2; >+ else if (is_nm_fault(intr_info) && >+ vcpu->arch.guest_fpu.fpstate->xfd) does this necessarily mean the #NM is caused by XFD? >+ event_data = vcpu->arch.guest_fpu.xfd_err; >+ >+ vmcs_write64(INJECTED_EVENT_DATA, event_data); >+ } >+ } >+ > vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info); > > vmx_clear_hlt(vcpu); >@@ -7226,7 +7247,8 @@ static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx) > static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu, > u32 idt_vectoring_info, > int instr_len_field, >- int error_code_field) >+ int error_code_field, >+ int event_data_field) event_data_field is used to indicate whether this is a "cancel". I may think it is better to simply use a boolean e.g., bool cancel. > { > u8 vector; > int type; >@@ -7260,6 +7282,37 @@ static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu, > vcpu->arch.event_exit_inst_len = vmcs_read32(instr_len_field); > fallthrough; > case INTR_TYPE_HARD_EXCEPTION: >+ if (kvm_is_fred_enabled(vcpu) && event_data_field) { >+ /* >+ * Save original-event data for being used as injected-event data. >+ */ Looks we also expect CPU will update CR2/DR6/XFD_ERR. this hunk looks to me just a paranoid check to ensure the cpu works as expected. if that's the case, I suggest documenting it a bit in the comment. >+ u64 event_data = vmcs_read64(event_data_field); >+ >+ switch (vector) { >+ case DB_VECTOR: >+ get_debugreg(vcpu->arch.dr6, 6); >+ WARN_ON(vcpu->arch.dr6 != (event_data ^ DR6_RESERVED)); >+ vcpu->arch.dr6 = event_data ^ DR6_RESERVED; >+ break; >+ case NM_VECTOR: >+ if (vcpu->arch.guest_fpu.fpstate->xfd) { >+ rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err); >+ WARN_ON(vcpu->arch.guest_fpu.xfd_err != event_data); >+ vcpu->arch.guest_fpu.xfd_err = event_data; >+ } else { >+ WARN_ON(event_data != 0); >+ } >+ break; >+ case PF_VECTOR: >+ WARN_ON(vcpu->arch.cr2 != event_data); >+ vcpu->arch.cr2 = event_data; >+ break; >+ default: >+ WARN_ON(event_data != 0); I am not sure if this WARN_ON() can be triggeded by nested VMX. It is legitimate for L1 VMM to inject any event w/ an event_data. FRED spec says: Section 5.2.1 specifies the event data that FRED event delivery of certain events saves on the stack. When FRED event delivery is used for an event injected by VM entry, the event data saved is the value of the injected-event-data field in the VMCS. This value is used instead of what is specified in Section 5.2.1 and is done for __ALL__ injected events using FRED event delivery >+ break; >+ } >+ } >+ > if (idt_vectoring_info & VECTORING_INFO_DELIVER_CODE_MASK) { > u32 err = vmcs_read32(error_code_field); > kvm_requeue_exception_e(vcpu, vector, err); >@@ -7279,9 +7332,11 @@ static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu, > > static void vmx_complete_interrupts(struct vcpu_vmx *vmx) > { >- __vmx_complete_interrupts(&vmx->vcpu, vmx->idt_vectoring_info, >+ __vmx_complete_interrupts(&vmx->vcpu, >+ vmx->idt_vectoring_info, > VM_EXIT_INSTRUCTION_LEN, >- IDT_VECTORING_ERROR_CODE); >+ IDT_VECTORING_ERROR_CODE, >+ ORIGINAL_EVENT_DATA); > } > > static void vmx_cancel_injection(struct kvm_vcpu *vcpu) >@@ -7289,7 +7344,8 @@ static void vmx_cancel_injection(struct kvm_vcpu *vcpu) > __vmx_complete_interrupts(vcpu, > vmcs_read32(VM_ENTRY_INTR_INFO_FIELD), > VM_ENTRY_INSTRUCTION_LEN, >- VM_ENTRY_EXCEPTION_ERROR_CODE); >+ VM_ENTRY_EXCEPTION_ERROR_CODE, >+ 0); > > vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0); > }
> >+ else if (is_nm_fault(intr_info) && > >+ vcpu->arch.guest_fpu.fpstate->xfd) > > does this necessarily mean the #NM is caused by XFD? Then the event data should be 0. Or I missed something obvious? I.e., it can be easily differentiated and we should just explicitly set it to 0. > > >+ event_data = vcpu->arch.guest_fpu.xfd_err; > >+ > >+ vmcs_write64(INJECTED_EVENT_DATA, event_data); > >+ } > >+ } > >+ > > vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info); > > > > vmx_clear_hlt(vcpu); > >@@ -7226,7 +7247,8 @@ static void vmx_recover_nmi_blocking(struct > >vcpu_vmx *vmx) static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu, > > u32 idt_vectoring_info, > > int instr_len_field, > >- int error_code_field) > >+ int error_code_field, > >+ int event_data_field) > > event_data_field is used to indicate whether this is a "cancel". I may think it is > better to simply use a boolean e.g., bool cancel. I'm fine with the idea if no objections. > > > > { > > u8 vector; > > int type; > >@@ -7260,6 +7282,37 @@ static void __vmx_complete_interrupts(struct > kvm_vcpu *vcpu, > > vcpu->arch.event_exit_inst_len = vmcs_read32(instr_len_field); > > fallthrough; > > case INTR_TYPE_HARD_EXCEPTION: > >+ if (kvm_is_fred_enabled(vcpu) && event_data_field) { > >+ /* > >+ * Save original-event data for being used as injected- > event data. > >+ */ > > Looks we also expect CPU will update CR2/DR6/XFD_ERR. this hunk looks to me > just a paranoid check to ensure the cpu works as expected. if that's the case, I > suggest documenting it a bit in the comment. These checks are not intended for hw, they make sure nVMX FRED is correctly implemented and catch regressions. And yes, in the early stage, I prefer to be paranoid. > > >+ u64 event_data = vmcs_read64(event_data_field); > >+ > >+ switch (vector) { > >+ case DB_VECTOR: > >+ get_debugreg(vcpu->arch.dr6, 6); > >+ WARN_ON(vcpu->arch.dr6 != (event_data ^ > DR6_RESERVED)); > >+ vcpu->arch.dr6 = event_data ^ DR6_RESERVED; > >+ break; > >+ case NM_VECTOR: > >+ if (vcpu->arch.guest_fpu.fpstate->xfd) { > >+ rdmsrl(MSR_IA32_XFD_ERR, vcpu- > >arch.guest_fpu.xfd_err); > >+ WARN_ON(vcpu- > >arch.guest_fpu.xfd_err != event_data); > >+ vcpu->arch.guest_fpu.xfd_err = > event_data; > >+ } else { > >+ WARN_ON(event_data != 0); > >+ } > >+ break; > >+ case PF_VECTOR: > >+ WARN_ON(vcpu->arch.cr2 != event_data); > >+ vcpu->arch.cr2 = event_data; > >+ break; > >+ default: > >+ WARN_ON(event_data != 0); > > I am not sure if this WARN_ON() can be triggeded by nested VMX. It is legitimate > for L1 VMM to inject any event w/ an event_data. > > FRED spec says: > > Section 5.2.1 specifies the event data that FRED event delivery of certain events > saves on the stack. When FRED event delivery is used for an event injected by VM > entry, the event data saved is the value of the injected-event-data field in the > VMCS. This value is used instead of what is specified in Section 5.2.1 and is done > for __ALL__ injected events using FRED event delivery 5.2.1 Saving Information on the Regular Stack also says: - For any other event, the event data are not currently defined and will be zero until they are. Or you mean something else?
On Tue, Nov 14, 2023 at 12:34:02PM +0800, Li, Xin3 wrote: >> >+ else if (is_nm_fault(intr_info) && >> >+ vcpu->arch.guest_fpu.fpstate->xfd) >> >> does this necessarily mean the #NM is caused by XFD? > >Then the event data should be 0. Or I missed something obvious? I.e., >it can be easily differentiated and we should just explicitly set it >to 0. vcpu->arch.guest_fpu.fpstate->xfd just means the guest is enabling XFD. I don't think we can conclude that this #NM is caused by XFD only from this. i.e., there may be some false positives. >> >+ u64 event_data = vmcs_read64(event_data_field); >> >+ >> >+ switch (vector) { >> >+ case DB_VECTOR: >> >+ get_debugreg(vcpu->arch.dr6, 6); >> >+ WARN_ON(vcpu->arch.dr6 != (event_data ^ >> DR6_RESERVED)); >> >+ vcpu->arch.dr6 = event_data ^ DR6_RESERVED; >> >+ break; >> >+ case NM_VECTOR: >> >+ if (vcpu->arch.guest_fpu.fpstate->xfd) { >> >+ rdmsrl(MSR_IA32_XFD_ERR, vcpu- >> >arch.guest_fpu.xfd_err); >> >+ WARN_ON(vcpu- >> >arch.guest_fpu.xfd_err != event_data); >> >+ vcpu->arch.guest_fpu.xfd_err = >> event_data; >> >+ } else { >> >+ WARN_ON(event_data != 0); >> >+ } >> >+ break; >> >+ case PF_VECTOR: >> >+ WARN_ON(vcpu->arch.cr2 != event_data); >> >+ vcpu->arch.cr2 = event_data; >> >+ break; >> >+ default: >> >+ WARN_ON(event_data != 0); >> >> I am not sure if this WARN_ON() can be triggeded by nested VMX. It is legitimate >> for L1 VMM to inject any event w/ an event_data. >> >> FRED spec says: >> >> Section 5.2.1 specifies the event data that FRED event delivery of certain events >> saves on the stack. When FRED event delivery is used for an event injected by VM >> entry, the event data saved is the value of the injected-event-data field in the >> VMCS. This value is used instead of what is specified in Section 5.2.1 and is done >> for __ALL__ injected events using FRED event delivery > >5.2.1 Saving Information on the Regular Stack also says: >- For any other event, the event data are not currently defined and will > be zero until they are. > >Or you mean something else? IIUC, L1 KVM can inject a nested exception whose vector isn't #DB, or #NM or #PF with a non-zero event_data to L2. If delivering the nested exception causes a VM-exit to L0 KVM, the assertion that event_data is always 0 for vectors other than #DB/#NM/#PF fails.
> >> >+ else if (is_nm_fault(intr_info) && > >> >+ vcpu->arch.guest_fpu.fpstate->xfd) > >> > >> does this necessarily mean the #NM is caused by XFD? > > > >Then the event data should be 0. Or I missed something obvious? I.e., > >it can be easily differentiated and we should just explicitly set it to > >0. > > vcpu->arch.guest_fpu.fpstate->xfd just means the guest is enabling XFD. > I don't think we can conclude that this #NM is caused by XFD only from this. i.e., > there may be some false positives. Then we should get 0 in event data. Otherwise, it is a bug in how we deal with IA32_XFD_ERR MSR, w/ or w/o FRED. > >> >+ default: > >> >+ WARN_ON(event_data != 0); > >> > >> I am not sure if this WARN_ON() can be triggeded by nested VMX. It is > >> legitimate for L1 VMM to inject any event w/ an event_data. > >> > >> FRED spec says: > >> > >> Section 5.2.1 specifies the event data that FRED event delivery of > >> certain events saves on the stack. When FRED event delivery is used > >> for an event injected by VM entry, the event data saved is the value > >> of the injected-event-data field in the VMCS. This value is used > >> instead of what is specified in Section 5.2.1 and is done for __ALL__ > >> injected events using FRED event delivery > > > >5.2.1 Saving Information on the Regular Stack also says: > >- For any other event, the event data are not currently defined and > >will > > be zero until they are. > > > >Or you mean something else? > > IIUC, L1 KVM can inject a nested exception whose vector isn't #DB, or #NM or #PF > with a non-zero event_data to L2. No, this is not allowed. > If delivering the nested exception causes a VM- > exit to L0 KVM, the assertion that event_data is always 0 for vectors other than > #DB/#NM/#PF fails.
>> >> >+ default: >> >> >+ WARN_ON(event_data != 0); >> >> >> >> I am not sure if this WARN_ON() can be triggeded by nested VMX. It is >> >> legitimate for L1 VMM to inject any event w/ an event_data. >> >> >> >> FRED spec says: >> >> >> >> Section 5.2.1 specifies the event data that FRED event delivery of >> >> certain events saves on the stack. When FRED event delivery is used >> >> for an event injected by VM entry, the event data saved is the value >> >> of the injected-event-data field in the VMCS. This value is used >> >> instead of what is specified in Section 5.2.1 and is done for __ALL__ >> >> injected events using FRED event delivery >> > >> >5.2.1 Saving Information on the Regular Stack also says: >> >- For any other event, the event data are not currently defined and >> >will >> > be zero until they are. >> > >> >Or you mean something else? >> >> IIUC, L1 KVM can inject a nested exception whose vector isn't #DB, or #NM or #PF >> with a non-zero event_data to L2. > >No, this is not allowed. How do you interpret the last sentence: Section 5.2.1 specifies the event data that FRED event delivery of certain events saves on the stack. When FRED event delivery is used for an event injected by VM entry, the event data saved is the value of the injected-event-data field in the VMCS. This value is used instead of what is specified in Section 5.2.1 and is done for __ALL__ injected events using FRED event delivery
> >> IIUC, L1 KVM can inject a nested exception whose vector isn't #DB, or > >> #NM or #PF with a non-zero event_data to L2. > > > >No, this is not allowed. > > How do you interpret the last sentence: > > Section 5.2.1 specifies the event data that FRED event delivery of > certain events saves on the stack. When FRED event delivery is used > for an event injected by VM entry, the event data saved is the value > of the injected-event-data field in the VMCS. This value is used > instead of what is specified in Section 5.2.1 and is done for __ALL__ > injected events using FRED event delivery To me, it means FRED event injection during VM entry simply pushes the value in the injected-event-data field of the VMCS as event data. But the event data definition should comply with Section 5.2.1. It is a forward compatibility issue otherwise.
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h index d54a1a1057b0..97729248e844 100644 --- a/arch/x86/include/asm/vmx.h +++ b/arch/x86/include/asm/vmx.h @@ -253,8 +253,12 @@ enum vmcs_field { PID_POINTER_TABLE_HIGH = 0x00002043, SECONDARY_VM_EXIT_CONTROLS = 0x00002044, SECONDARY_VM_EXIT_CONTROLS_HIGH = 0x00002045, + INJECTED_EVENT_DATA = 0x00002052, + INJECTED_EVENT_DATA_HIGH = 0x00002053, GUEST_PHYSICAL_ADDRESS = 0x00002400, GUEST_PHYSICAL_ADDRESS_HIGH = 0x00002401, + ORIGINAL_EVENT_DATA = 0x00002404, + ORIGINAL_EVENT_DATA_HIGH = 0x00002405, VMCS_LINK_POINTER = 0x00002800, VMCS_LINK_POINTER_HIGH = 0x00002801, GUEST_IA32_DEBUGCTL = 0x00002802, diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 58d01e845804..67fd4a56d031 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1880,9 +1880,30 @@ static void vmx_inject_exception(struct kvm_vcpu *vcpu) vmcs_write32(VM_ENTRY_INSTRUCTION_LEN, vmx->vcpu.arch.event_exit_inst_len); intr_info |= INTR_TYPE_SOFT_EXCEPTION; - } else + } else { intr_info |= INTR_TYPE_HARD_EXCEPTION; + if (kvm_is_fred_enabled(vcpu)) { + u64 event_data = 0; + + if (is_debug(intr_info)) + /* + * Compared to DR6, FRED #DB event data saved on + * the stack frame have bits 4 ~ 11 and 16 ~ 31 + * inverted, i.e., + * fred_db_event_data = dr6 ^ 0xFFFF0FF0UL + */ + event_data = vcpu->arch.dr6 ^ DR6_RESERVED; + else if (is_page_fault(intr_info)) + event_data = vcpu->arch.cr2; + else if (is_nm_fault(intr_info) && + vcpu->arch.guest_fpu.fpstate->xfd) + event_data = vcpu->arch.guest_fpu.xfd_err; + + vmcs_write64(INJECTED_EVENT_DATA, event_data); + } + } + vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, intr_info); vmx_clear_hlt(vcpu); @@ -7226,7 +7247,8 @@ static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx) static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu, u32 idt_vectoring_info, int instr_len_field, - int error_code_field) + int error_code_field, + int event_data_field) { u8 vector; int type; @@ -7260,6 +7282,37 @@ static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu, vcpu->arch.event_exit_inst_len = vmcs_read32(instr_len_field); fallthrough; case INTR_TYPE_HARD_EXCEPTION: + if (kvm_is_fred_enabled(vcpu) && event_data_field) { + /* + * Save original-event data for being used as injected-event data. + */ + u64 event_data = vmcs_read64(event_data_field); + + switch (vector) { + case DB_VECTOR: + get_debugreg(vcpu->arch.dr6, 6); + WARN_ON(vcpu->arch.dr6 != (event_data ^ DR6_RESERVED)); + vcpu->arch.dr6 = event_data ^ DR6_RESERVED; + break; + case NM_VECTOR: + if (vcpu->arch.guest_fpu.fpstate->xfd) { + rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err); + WARN_ON(vcpu->arch.guest_fpu.xfd_err != event_data); + vcpu->arch.guest_fpu.xfd_err = event_data; + } else { + WARN_ON(event_data != 0); + } + break; + case PF_VECTOR: + WARN_ON(vcpu->arch.cr2 != event_data); + vcpu->arch.cr2 = event_data; + break; + default: + WARN_ON(event_data != 0); + break; + } + } + if (idt_vectoring_info & VECTORING_INFO_DELIVER_CODE_MASK) { u32 err = vmcs_read32(error_code_field); kvm_requeue_exception_e(vcpu, vector, err); @@ -7279,9 +7332,11 @@ static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu, static void vmx_complete_interrupts(struct vcpu_vmx *vmx) { - __vmx_complete_interrupts(&vmx->vcpu, vmx->idt_vectoring_info, + __vmx_complete_interrupts(&vmx->vcpu, + vmx->idt_vectoring_info, VM_EXIT_INSTRUCTION_LEN, - IDT_VECTORING_ERROR_CODE); + IDT_VECTORING_ERROR_CODE, + ORIGINAL_EVENT_DATA); } static void vmx_cancel_injection(struct kvm_vcpu *vcpu) @@ -7289,7 +7344,8 @@ static void vmx_cancel_injection(struct kvm_vcpu *vcpu) __vmx_complete_interrupts(vcpu, vmcs_read32(VM_ENTRY_INTR_INFO_FIELD), VM_ENTRY_INSTRUCTION_LEN, - VM_ENTRY_EXCEPTION_ERROR_CODE); + VM_ENTRY_EXCEPTION_ERROR_CODE, + 0); vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0); } @@ -7406,6 +7462,24 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu, vmx_disable_fb_clear(vmx); + /* + * %cr2 needs to be saved after a VM exit and restored before a VM + * entry in case a VM exit happens immediately after delivery of a + * guest #PF but before guest reads %cr2. + * + * A FRED guest should read its #PF faulting linear address from + * the event data field in its FRED stack frame instead of %cr2. + * But the FRED 5.0 spec still requires a FRED CPU to update %cr2 + * in the normal way, thus %cr2 is still updated even for a FRED + * guest. + * + * Note, an NMI could interrupt KVM: + * 1) after VM exit but before CR2 is saved. + * 2) after CR2 is restored but before VM entry. + * And a #PF could happen durng NMI handlng, which overwrites %cr2. + * Thus exc_nmi() should save and restore %cr2 upon entering and + * before leaving to make sure %cr2 not corrupted. + */ if (vcpu->arch.cr2 != native_read_cr2()) native_write_cr2(vcpu->arch.cr2); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c5a55810647f..d190bfc63fc4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -680,8 +680,14 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu, vcpu->arch.exception.injected = true; if (WARN_ON_ONCE(has_payload)) { /* - * A reinjected event has already - * delivered its payload. + * For a reinjected event, KVM delivers its + * payload through: + * #PF: save %cr2 into arch.cr2 immediately + * after VM exits. + * #DB: save %dr6 into arch.dr6 later in + * sync_dirty_debug_regs(). + * + * For FRED guest, see __vmx_complete_interrupts(). */ has_payload = false; payload = 0;